Of all apex predators, the white shark Carchardon carcharias (commonly known as the great white) is perhaps the most fascinating. The potential danger from (very rare) human interaction has embedded the species in our national consciousness.

Debate as to the size and status of the white shark populations across the globe is both vigorous and often contested, and it is fair to say we have never had an accurate picture. Now, for the first time we estimate that the total number of adult sharks across the Australasian region is around 2,210. We’re lacking data on juvenile sharks in one region so it’s difficult to say what the total Australasian population is, but it’s likely to be in excess of 8,000-10,000 animals.

CSIRO researchers working with Australian and New Zealand scientists in the National Environmental Science Program have used world-first genetic analysis to investigate white shark populations. The results of this project, published on Thursday in the journal Scientific Reports, are the first estimates of white shark adult population size, trend and survival rates for the Australasian region.

One fish, two fish…

The widely used aphorism in marine and particularly fisheries modelling is that counting fish is like counting trees, but you can’t see them and they move around all the time.

Until now, researchers have had to rely on patchy sources, like historical catch data. The various shark control programs do not provide usable data on relative density over time. We do have information on white shark migration and population structure from electronic tagging and previous genetic studies, but these don’t tell us about shark numbers.

To address this key problem we worked with colleagues across Australia and New Zealand to use a highly novel method called close-kin mark-recapture, first developed by CSIRO in the late 2000s to monitor southern bluefin tuna.

Close-kin mark-recapture first involves taking a tissue sample from a shark, alive or dead, obtaining a genetic profile of the animal, and than comparing it to all the other sharks and asking: are these sharks related, and if so how are they related?

Due to a number of factors, it is easier to take genetic samples from juvenile white sharks (in the 3.5 to 4m or less range) than from adults.

In the first phase, we compared the genetic data from juvenile white sharks to look for half-sibling pairs – animals who shared either a mother or a father. The half-siblings are the close-kin side of the problem. The chances of finding these pairs in the samples is determined by (a) the size of the adult population, and (b) the survival rate of adult sharks.

Higher numbers of sharks, or sharks with low survival rates, make it less likely to find siblings in the samples.

This linkage between a specific type of relatedness (half brothers or sisters) and the size and survival rate of the adult population is the mark-recapture side of the equation. In traditional wildlife tagging studies, we “mark” an animal in some way (physically or in terms of visual or genetic ID) and try to “recapture” it again sometime in the future.

The mark-recapture principle is exactly the same with this method. The key difference is that a juvenile shark carries the “mark” of its parent within its DNA, which is “recaptured” when you find a half-sibling pair. Find enough of these half-siblings, and you can estimate both adult numbers and survival rates.

Population

Currently, we believe there are two main populations of white shark in the Australasian region: the “Eastern” population, which is basically everything to the east of Bass Strait (including New Zealand), and the “Southern-Western” population, which appears to range from west of Bass Strait, around the South Australia and West Australia coasts as far north as Ningaloo Reef.

CSIRO, Author provided

As part of phase one of the project we looked for half-siblings among 75 Eastern Australasian juvenile sharks and found 20. To give this some context, 75 samples permits 2,775 unique comparisons between animals. So less than 1% of those comparisons were siblings. We estimated that the number of adult sharks to be around 470 (with a range of 280-650), with at least 90% surviving from one year to the next. Given limited data there was no precise information on adult population trend.

The close-kin approach can only tell us about the adult population, however. To extend these estimates to total population size, we need to know something about the survival rate of juvenile sharks. Using data from around 70 juvenile sharks fitted with acoustic emitters, archived under Australia’s Integrated Marine Observing System, we estimated that juvenile sharks had an annual survival rate of around 73%.

Combining these juvenile survival estimates with the adult abundance and survival information from the close-kin analyses we estimated there to be around 4,060 (and a range of 2,500-6,750) white sharks in the whole Eastern population.

After obtaining these results from the initial data, we moved onto phase two of the project. We collected and processed more samples to obtain both more data for the Eastern population, and enough samples and half-sibling matches to estimate the adult population size in the Southern-Western region. In the East we now have 214 juvenile samples, and found 73 half-siblings; in the Southern-Western case we now have 175 samples, and found 27 half-siblings.

The revised estimates of adult population size in the East were around 750 (with a range of 470-1,030) and annual survival probabilities of 93%. Revised estimates of total population size in the Eastern region were around 5,460 (with a range of 2,909-12,802).

Our initial estimates of the Southern-Western adult population were around 1,460 (with a range of 760-2,250) and that survival probabilities were very high (in the 90% and above range, as for the East). So these estimates suggest there are almost twice as many adult white sharks in the Southern-Western population relative to the East.

We found that in both populations the adult population trend since protection has been essentially flat, with no evidence for a substantial increase or decrease. However, the picture is more uncertain when it comes to estimating population changes for younger white sharks.

White sharks take 12-15 years to mature. Assuming protection of the species reduced the juvenile mortality rate, then any such effect will not be apparent in the adult population until the next 5-10 years.

Balancing the conflicting goals of conservation and human protection is at times difficult and contentious. But, unquestionably, without being able to monitor populations effectively there is no way to resolve these questions.

Now we can monitor juveniles through electronic tagging programs, and keep track of adult populations with the close-kin method, we should finally have solved the problem of how to track the population size and status of this iconic predator.

In recent days, several local landowners have blocked the Owers Corner end of the famed Kokoda Track in Papua New Guinea. They claimed they would stop tourists from accessing the track until the PNG government meets their demands.

According to their spokesman James Enage, government promises of economic benefits have not been fulfilled. Understaffed health centres and lack of education funding are causing great resentment among the local population. This is despite the establishment of the Kokoda Initiative, a joint undertaking between the Australian and Papua New Guinean governments that aims to “improve the livelihoods of communities along the track”.

The closure of the Kokoda Track by local landowners is not unprecedented; a similar closure took place at the Kokoda end in 2009.

The current blockade is a product of the complex political and economic issues affecting PNG, which is still dealing with the consequences of a controversial election late last year. It also highlights the complicated relationship between Australian war memory and its developmental assistance to a former colonial possession.

Australian aid preserving ‘hallowed ground’

The Kokoda Track experienced a resurgence of Australian attention following Prime Minister Paul Keating’s 1992 visit. He famously kissed the “hallowed ground” of the former battlefield.

In the 2000s, increasing numbers of Australian visitors sought to make the arduous trek, retracing the footsteps of former Australian soldiers. But with increased visitors came increased pressure on the local population.

In response to growing local discontent (which resulted in the 2009 blockade), the Kokoda Initiative Development Program was established in 2010 to improve living standards in areas along the track. The program includes educational services, provision of health supplies and infrastructure, and maintenance of the track itself.

Despite Australian government claims to have established several of these services, the protests at Owers Corner suggests that Australian aid is not making its way to the intended recipients. This is a common issue in aid delivery, particularly in remote areas such as those along the Kokoda Track.

Maintaining the Kokoda Initiative’s effective implementation is vital to ensuring the local population is able to enjoy the benefits of increased Australian visits to the track.

PNG’s health crisis

Compounding the problems with Australian aid are domestic issues related to the provision of health services throughout PNG. According to the country’s shadow minister for health and HIV/AIDS, Joseph Yopyyopi, PNG is suffering from a “health crisis”. Health workers are going without pay, and numerous hospitals are running out of basic supplies and medicines.

All of this comes despite Prime Minister Peter O’Neill’s promise of free education and health for all. But, if anything, the PNG population’s health has been in decline since O’Neill came to power. There is also little prospect of things changing quickly, given the unstable political situation following the 2017 election.

The Lowy Institute’s Jonathan Pryke and Paul Barker argue that Papua New Guineans experience lower health standards now than during the Australian colonial period prior to 1975. They suggest medical clinics are in crisis.

It is little surprise, then, that local communities suffering from the lack of health and education services have resorted to protests.

Striking a balance

Targeting the entry to a “sacred place” for Australians can be seen as a calculated move on the part of local PNG landowners. By preventing Australians from visiting the Kokoda Track, it is more likely that their grievances will be met.

It also points to a broader issue in PNG, as the problems people like Enage are facing are not isolated. Significant improvements are needed to improve basic services throughout PNG – not just along the Kokoda Track.

PNG continues to require significant amounts of Australian aid. According to 2017-18 budget estimates, PNG is to receive more than A$500 million, making it Australia’s largest aid recipient. This situation is very similar to the mid-1970s, when the colonial grant to PNG constituted two-thirds of Australian “aid”.

Australia’s Department of Foreign Affairs and Trade claims it is providing “tangible and lasting benefits” to the local communities surrounding the Kokoda Track. The blockade suggests this is not the case. Improved aid provision and governance within PNG is required to meet the needs of the people living near this “sacred place”.

In Indonesia, more than 197 million people live within 100km of a volcano, including more than 8.6 million inside a 10km radius.

The country has a record of some of the most deadly volcanic eruptions in history, and right now there are ongoing eruptions at the Agung, Sinabung and Dukono volcanoes. But other volcanoes in the region are active too, including Kadovar in Papua New Guinea, Mayon in the Philippines, and Kusatsu-Shiranesan in Japan.

Although it all seems to be happening at once, it’s normal for the Asia-Pacific region to have frequent earthquake and volcanic activity.

But we still need to keep a close eye on things, and local volcanic authorities are monitoring activity to manage risks and evacuations adequately.

These volcanoes are part of the Pacific “Ring of Fire”, a horseshoe-shaped belt of earthquakes and volcanoes that runs for some 40,000km, roughly around the edge of the Pacific Ocean. The Ring stretches from South America, up to North America and across the Bering straight, and down through Japan, the Philippines, Papua New Guinea, Vanuatu and New Zealand. It generates around 90% of the world’s earthquakes and contains 75% of its active volcanoes.

Here are the volcanoes on my Asia-Pacific watch list this week.

Agung, Bali, Indonesia

Mount Agung in Bali has been highly scrutinised for the past few months, largely because of Bali’s popularity as a tourist destination.

After a series of volcanic earthquakes (more than 1,000 per day at its peak), eruptions began on November 21, 2017.

In the evening of January 19 an explosion of fire (known as a “strombolian” eruption) ejected glowing rocks up to 1km from the crater. The alert level remains at the highest level, with an exclusion zone in place.

There have been very few issues for tourists visiting Bali so far, apart from a temporary closure of Denpasar airport in late November 2017. However, thousands of Agung’s local residents are still displaced from their homes, with many still stationed in evacuation centres. It remains uncertain when those living closest will be able to return home.

Sinabung, Sumatra, Indonesia

Sinabung volcano awoke in 2010 after a 400-year sleep, and is currently one of the most active volcanoes in Indonesia. It has been pretty much in constant eruption since September 2013, and there are still frequent volcanic earthquakes.

Eruptions have produced ash plumes reaching as high as 11km into the atmosphere, as well as ash fall and lava flows. There have also been volcanic mudflows (“lahars”) and fast-moving, hot flows of gas, ash and rock fragments (“pyroclastic flows”), which have killed 25 people.

The initial activity in 2010 saw around 30,000 people evacuated. In August last year the Indonesian National Disaster Management Authority (BNPB) reported that there were 7,214 people displaced, and a further 2,863 living in refugee camps. For the locals, life seemingly goes on in the midst of eruptions.

The alert level currently remains at 4 (on a scale of 1-4), with exclusion zones of 3-7km around the volcano.

Mayon, Luzon, Philippines

Mayon, around 330km southeast of Manila, is a picture-perfect volcano with its steep-sided conical cone, typical of stratovolcanoes. It is one of the most active volcanoes in the Philippines, with 24 confirmed eruptive periods in the past 100 years. Mayon’s most violent eruption in 1814 killed more than 1,200 people and destroyed several towns.

The recent eruption began on January 13, 2018, and is continuing, with several episodes of dramatic lava fountaining, one lasting 74 minutes.

Eruptions during January 23-29 generated 3-5km-high ash plumes and multiple pyroclastic flows, which travelled more than 5km down drainage channels. The alert is at level 4 (on a scale of 1 to 5) and an 8km danger zone is in place.

Lava flows have currently made their way up to 4.5km down river valleys from the summit crater.

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) estimated on January 27 that the total volume of material deposited from ash fall and pyroclastic flows amounted to 10.5 million cubic metres. Remobilisation of this loose volcanic material by rainfall to form volcanic mudflows is a major concern.

According to news articles, more than 75,000 people have been evacuated, along with the temporary closure of Legazpi airport around 15km away.

Kadovar, Papua New Guinea

Until January 2018, when it began erupting, I hadn’t heard of Kadovar. It’s a 2km-wide, 365m-high emergent summit of a stratovolcano off the coast of Papua New Guinea.

The volcano had no confirmed historic eruptions before 2018. However, it is possible that William Dampier, a 17th-century pirate and later maritime adventurer, witnessed an eruption at Kadovar during a voyage in search of Terra Australis.

Activity began on January 5, 2018, with rising plumes of ash and steam from the volcano. The island’s inhabitants, some literally living on the crater rim, began evacuating at that time. People were initially taken by boat to neighbouring Blup Blup island but then to the mainland along with other nearby islanders, due to the close proximity of the eruption and logistics of providing people with supplies.

The Rabaul Volcano Observatory reported that activity significantly escalated on January 12, with a large explosive eruption and volcanic rocks ejected to the south. Large amounts of sulfur dioxide have been detected since January 8, and continue to be released along with ash and steam plumes. A lava “dome” has been observed glowing at night.

The impact from the eruption is not just confined to those on Kadovar and nearby islands, with satellite imagery tracking an ash plume from Kadovar travelling over tens of kilometres.

Kusatsu-Shirane, Honshu Japan

On January 23, 2018, an eruption occurred at Kusatsu-Shirane volcano without any prior warning, catching Japan’s Meteorological Agency and volcanic experts, not to mention the skiers on the volcano, by surprise.

The ejected volcanic rocks, which landed up to 1km away from the vent, injured several people. A member of the Ground Self-Defence Force who was skiing in a training exercise was killed.

The Japan Meteorological Agency has since analysed the deposits of the eruption and state that there was no new magma erupted on January 23.

Volcanic rocks were ejected from the Kusatsu-Shirane volcano.

Japan has more than 100 active volcanoes, with many monitored 24/7 by Japan’s Meteorological Agency.

Living near volcanoes

Indonesia, the Philippines and Japan have the greatest numbers of people living within 100km of their volcanoes. The populations of small volcanic island nations, such as Tonga and Samoa, almost all live within 100km.

The top 10 countries for population within 100 km of a volcano (left) and the top ten countries (area over 31,415 km²) for percentage of the total population (right).Sarah Brown and co-authors.

Indonesia has the greatest total population located within 10km (more than 8.6 million), 30km (more than 68 million) and 100km (more than 179 million), and a record of some of the most deadly volcanic eruptions in history.

The eruption of Tambora in 1812-15, was the largest eruption in the last 10,000 years and killed around 100,000 Indonesians (due to the eruption and the ensuing famine). The infamous eruption of Krakatau (Krakatoa) killed an estimated 35,000 people, almost all due to volcanic-generated tsunamis. Volcanic mudflows (lahars) generated by the eruptions of 1586 and 1919 at Kelut (Kelud) in Java took the lives of 10,000 and 5,000 people, respectively.

Keeping watch on the world’s volcanoes is a big job for the local volcanic agencies. This is particularly true when volcanoes erupt for the first time in history (Kadovar is a good example) or there were no warning signals before eruption, as at Kusatsu-Shirane.